Metallic aircraft component

Abstract

The invention relates to metallic aircraft components which can preferably be used for aircraft structures in the fuselage region. A damage-tolerant design is usual for aircraft components in the fuselage region. It is the object of the invention to provide metallic components in which metal sheets are connected to one another by weld seams which have an improved damage tolerance behavior and fatigue crack propagation behavior. In an aircraft component in accordance with the invention, at least two metal sheets are welded to one another as butt joints. The centerline of the join line of the weld seam is predetermined by the outer edge contour of the metal sheets connected to one another. In this connection, it is formed deviant from a continuously straight line shape such that the total length of the weld seam is increased by changes in direction periodically occurring at the edge contours engaging into one another in a complementary manner.

1. A metallic aircraft component, comprising:
 at least two metal sheets are connected to one another by means of a weld seam made as a butt joint, wherein a centerline of a join line of the weld seam is predetermined by an outer edge contour of the metal sheets connected to one another at respective edge contours and, deviating from a continuously straight line shape, wherein changes in direction increasing a total length of the weld seam are provided periodically at the two edge contours of the metal sheets engaging into one another in complementary manner wherein a periodically formed edge contour with amplitude A has a wavelength λ in the range of 0.1≦A/λ≦2 and the weld seam is formed such that, changes in direction of the weld seam within a join zone, occur in a manner that a path extending in a straight line across the join zone has a length Lmax which is smaller than a quotient of a critical crack length a c  specific to the component and an improvement factor, s that corresponds to a degree of improvement in damage tolerance of the weld seam as compared to damage tolerance of a continuous straight line weld seam formed when the two metal sheets are welded together in the continuous straight line weld seam with a same joining method as the weld seam. 
 
     
     
       2. A component in accordance with  claim 1 , wherein the edge contour of the metal sheets is shaped as one or more of a wave, sawtooth curved at vertices, meander, arcuate, trapezoidal comprising segments extending alternately in curved and straight-line form. 
     
     
       3. A component in accordance with  claim 1 , wherein a metal sheet thickness of the metal sheets is increased in the region of the edge contour. 
     
     
       4. A component in accordance with  claim 3 , wherein the metal sheet thickness is increased around the centerline of the join line to a width bs 1  of 2.4*A≦bs 1 ≦5*A wherein A is the amplitude of a periodic shape formed by the edge contours. 
     
     
       5. A component in accordance with  claim 3 , wherein a metal sheet thickness of each of the two metal sheets is gradually increased from an edge distal to the weld seam in a direction towards respective edge contours of the two metal sheets. 
     
     
       6. A component in accordance with  claim 3 , wherein the increased thickness is achieved with a skin field base. 
     
     
       7. A component in accordance with  claim 1 , wherein a skin field base is formed with a geometrical design at each of the metal sheets matched to the edge contour of the metal sheets. 
     
     
       8. A component in accordance with  claim 7 , wherein the skin field base has a constant width bs 2  at the respective metal sheet of each of the two sheets. 
     
     
       9. A component in accordance with  claim 1 , wherein when a skin field base is present, Lmax is smaller than a quotient of a product of a critical crack length a c  specific to the component with a base factor k and the improvement factor, s, wherein k≦m*[(h s +t)t 2 ) with 0.6<m≦1, h s  corresponds to a height of a skin field base, t is thickness of the metal sheets. 
     
     
       10. A component in accordance with  claim 1 , wherein the periodically formed edge contour has an amplitude A≧5 mm with respect to a line of symmetry of a centerline of the join line. 
     
     
       11. A component in accordance with  claim 1 , wherein the weld seam is made with a join zone having a width b Fz  in the range from 2 to 10 mm. 
     
     
       12. A component in accordance with  claim 1 , wherein a line of symmetry of a centerline of the join line has a shape deviating from a straight line at least regionally. 
     
     
       13. A component according to  claim 1 , wherein the critical crack length a c  in a direction of fatigue crack propagation can be determined by
     a   c   =a   cGW *( K   cFz   /K   cGW ) 2    
 
       where k cFz  is critical stress intensity factor for failure of a most unfavorable material state in a join zone for a given strain case; K cGW  is a critical stress intensity factor for a base material of the metal sheets for the given strain case and a cGW  is a critical crack length of a base material for a respective component geometry and the given strain case. 
     
     
       14. A component in accordance with  claim 1 , wherein the improvement factor s is larger than 1.2. 
     
     
       15. A metallic aircraft component comprising:
 at least two metal sheets connected to one another by a weld seam made as a butt joint, wherein a centerline of a join line of the weld seam is predetermined by an outer edge contour of the metal sheets connected to one another at respective edge contours and, deviating from a continuously straight line shape so that changes in direction increasing a total length of the weld seam are provided periodically at the two edge contours of the metal sheets engaging into one another in complementary manner and the weld seam is formed such that changes in direction of the weld seam within a join zone, occur in a manner that a path extending in a straight line across the join zone has a length Lmax which is smaller than a quotient of a critical crack length a c  specific to the component and an improvement factor, s that corresponds to a degree of improvement in damage tolerance of the weld seam as compared to damage tolerance of a continuous straight line weld seam formed when the two metal sheets are welded together in the continuous straight line weld seam with a same joining method as the weld seam; and 
 a doubler element connected in a firmly bonded manner to the metal sheets for reinforcement in the region of the weld seam and a width of the doubler element is in a range of 2.4*A to 6 *A wherein A is an amplitude of a periodic shape formed by the edge contours. 
 
     
     
       16. A metallic aircraft component comprising:
 at least two metal sheets connected to one another by a weld seam made as a butt joint, wherein a centerline of a join line of the weld seam is predetermined by an outer edge contour of the metal sheets connected to one another at respective edge contours and, deviating from a continuously straight line shape, so that changes in direction increasing a total length of the weld seam are provided periodically at the two edge contours of the metal sheets engaging one another in a complementary manner and the weld seam is formed such that changes in direction of the weld seam within a join zone, occur in a manner that a path extending in a straight line across the join zone has a length Lmax which is smaller than a quotient of a critical crack length a c  specific to the component and an improvement factor, s that corresponds to a degree of improvement in damage tolerance of the weld seam as compared to damage tolerance of a continuous straight line weld seam formed when the two metal sheets are welded together in the continuous straight line weld seam with a same joining method as the weld seam and one or more of an amplitude A and a wavelength λ of a periodically shaped edge contour is varied along a line of symmetry of a centerline of the join line.